### Please describe the problem.
When using git annex forget to clear the git-annex branch, syncing these changes does not result in clearing the git-annex branches of other remotes. Instead, these branches are only appended to with the commit starting the new branch, and when sync is run on the originating repo, the forget is undone.

### What steps will reproduce the problem?
1. `git annex forget --drop-dead`
2. (on remote) `git annex sync (repo where forget was run)`
3. (on starting repo) `git annex sync *remote*`

### What version of git-annex are you using? On what operating system?

    git-annex version: 8.20210223
    build flags: Assistant Webapp Pairing Inotify DBus DesktopNotify TorrentParser MagicMime Feeds Testsuite S3 WebDAV
    dependency versions: aws-0.22 bloomfilter-2.0.1.0 cryptonite-0.26 DAV-1.3.4 feed-1.3.0.1 ghc-8.8.4 http-client-0.6.4.1 persistent-sqlite-2.10.6.2 torrent-10000.1.1 uuid-1.3.13 yesod-1.6.1.0
    key/value backends: SHA256E SHA256 SHA512E SHA512 SHA224E SHA224 SHA384E SHA384 SHA3_256E SHA3_256 SHA3_512E SHA3_512 SHA3_224E SHA3_224 SHA3_384E SHA3_384 SKEIN256E SKEIN256 SKEIN512E SKEIN512 BLAKE2B256E BLAKE2B256 BLAKE2B512E BLAKE2B512 BLAKE2B160E BLAKE2B160 BLAKE2B224E BLAKE2B224 BLAKE2B384E BLAKE2B384 BLAKE2BP512E BLAKE2BP512 BLAKE2S256E BLAKE2S256 BLAKE2S160E BLAKE2S160 BLAKE2S224E BLAKE2S224 BLAKE2SP256E BLAKE2SP256 BLAKE2SP224E BLAKE2SP224 SHA1E SHA1 MD5E MD5 WORM URL X*
    remote types: git gcrypt p2p S3 bup directory rsync web bittorrent webdav adb tahoe glacier ddar git-lfs httpalso borg hook external
    operating system: linux x86_64
    supported repository versions: 8
    upgrade supported from repository versions: 0 1 2 3 4 5 6 7
    local repository version: 8

### Please provide any additional information below.

`git annex sync --cleanup` before sync was ineffective

There is no error log per se, git annex thinks everything went well.

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)
Aside from this, best thing ever.

> [[fixed|done]] back in 2022 --[[Joey]]
